How do I combine multiple calculations in MySQL unsing a single SQL statement?

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Hi guys,
I´m new to MySQL , so I would need some help. I´m writing my master thesis where I need to use SQL statements in order to get data from MySQL into a visualization software (software is called tableau) but I´m totally swamped :( would really appreciate your help!! Thanks a lot in advance! Best, Désirée
Here is my question: how do I get the following 4 calculations in one SQL statement:
• Database: is called foto
• The table rate_changes: contains following variables:
o Is_trial
o Is_conversion
o Is_churn
o Is_upgrade
o Is_downgrade
o Id
o Photographer_id
o Qualification
o Marketing_channel_id
o Kid
o Affiliate_id
o Old_rate_id
o New_rate_id
o Created
In order to calculate the # subscribers I need to do the following calculations:
(I write it down in a kind of meta language which is just a mix of SQL and the description of what I want to do, because I don´t know the correct SQL code)
Calculation 1:

SQL

Select count (foto.rate_changes.photographer_id)
From foto.rate_changes
Where foto.rate_changes.is_conversion = 1;

Calculation 2:

SQL

Select count (foto.rate_changes.photographer_id)
From foto.rate_changes
Where foto.rate_changes.is_churn= 1;

Calculation 3: result (calculation 1) – result (calculation 2)
Calculation 4: running sum of calculation 3 -->then you have the # subscribers per month

Posted 4-Apr-14 0:47am

Desmodireeic

Updated 4-Apr-14 6:50am

Maciej Los

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Maciej Los 4-Apr-14 12:49pm

What have you done till now? Where are you stuck?

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Maciej Los · Accepted Answer · 2014-04-04T08:20:00

Have you tried something similar to:

SQL

SELECT FT.Calculation1, FT.Calculation2, FT.Calculation1 - FT.Calculation2 AS Calculation3
FROM ((
   SELECT COUNT(foto.rate_changes.photographer_id) AS Calculation1
   FROM foto.rate_changes 
   WHERE foto.rate_changes.is_conversion = 1) AS t1
   INNER JOIN (
       SELECT COUNT(foto.rate_changes.photographer_id) AS Calculation2
       FROM foto.rate_changes
       WHERE foto.rate_changes.is_churn= 1) AS t2
   ON t1.Id = t2.Id) AS FT